Barda, O. | Search bioRxiv

bioRxiv2021

IQD1 involvement in hormonal signaling and general defense responses against Botrytis cinerea

IQ Domain 1 (IQD1) is a novel calmodulin-binding protein in A. thaliana, which was found to be a positive regulator of glucosinolate (GS) accumulation and plant defense responses against insects. We demonstrate here that the IQD1 overexpressing line (IQD1OXP) is more resistant also to the necrotrophic fungus Botrytis cinerea, whereas an IQD1 knockout line (iqd1-1) is much more sensitive. Furthermore, we show that IQD1 is upregulated by Jasmonic acid (JA) and downregulated by Salicylic acid (SA). Comparison of whole transcriptome expression between iqd1-1 and wild type revealed a substantial downregulation of genes involved in plant defense and hormone regulation. Further examination revealed a marked reduction of SA/JA signaling and increase in ethylene signaling genes in the iqd1-1 line. Moreover, quantification of SA, JA and abscisic acids in IQD1OXP and iqd1-1lines compared to WT showed a significant reduction in endogenous JA levels in the knockout line simultaneously with increased SA levels. Epistasis relations between IQD1OXP and mutants defective in plant-hormone signaling indicated that IQD1 acts upstream or parallel to the hormonal pathways (JA/ET and SA) in defense response against B. cinerea and in regulating GS accumulation and it is dependent on JAR1 controlling indole glucosinolate accumulation. As a whole, our results suggest that IQD1 is an important defensive protein against Botrytis cinerea in A. thaliana and is integrated into several important pathways such as plant microbe perception and hormone signaling. SIGNIFICANCE STATEMENTIQD1 is involved in glucosinolate accumulation and in general defense responses. JA activates IQD1 that acts upstream or parallel to JA/ET and SA signaling pathway while controlling glucosinolate accumulation and defense against Botrytis cinerea and it is dependent on JAR1 controlling indole glucosinolate accumulation.

plant biology↗

bioRxiv2020

Sensing stress responses in potato with whole-plant redox imaging

Environmental stresses are among the major factors that limit crop productivity and plant growth. Plant exposure to various abiotic stress, such as drought, cold temperatures, or high light, results in overproduction of reactive oxygen species (ROS). To avoid oxidative damage, critical mechanisms for their detoxification have evolved, consisting of ROS-scavenging enzymes and small antioxidant molecules, such as glutathione (GSH) and ascorbate. Thus, monitoring redox changes with high spatial and temporal resolution is critical for understanding oxidative stress signaling and has the potential to enable early detection of stress responses in crop plants. In this work, potato plants ( Solanum tuberosum) expressing a chloroplast-targeted reduction-oxidation-sensitive green fluorescent protein2 (roGFP2) were generated to report the redox potential of the glutathione (EGSH) in the chloroplast stroma. By applying whole-plant fluorescence imaging, we mapped alteration in the chloroplast EGSH under several stress conditions including, high-light, cold and drought. Extremely high increase in chloroplast EGSH was observed under the combination of high-light and low temperatures, conditions that specifically induce PSI photoinhibition. Intriguingly, whole-plant ratiometric imaging analysis noted a higher reduced state in newly developed as compared to mature leaves, suggesting a graded stress sensitivity as part of the plant strategies for coping with stress conditions. The presented observations suggest that whole-plant redox imaging can serve as a powerful tool for the basic understanding of plant stress responses as well as for applied agricultural research, such as improving phenotyping capabilities in breeding programs and early detection of stress responses in the field.

plant biology↗